Investigation of seaweed derivative iota-carrageenan based biopolymer electrolytes with lithium trifluoromethanesulfonate

In the present work, iota-carrageenan (i-carrageenan) biopolymer derived from edible seaweed has been chosen as the host polymer material for battery electrolyte. Ionic salt of lithium trifluoromethanesulfonate (LiCF3SO3) commonly known as lithium triflate has been added with the host polymer as a source of charge carriers. The polymer membranes of 1.0 g i-carrageenan with LiCF3SO3 of various compositions (0.1 wt% to 0.5 wt%) have been prepared by solution casting technique. X-ray diffraction (XRD) results indicate the enhancement in amorphous nature of polymer membranes due to the addition of LiCF3SO3. Complex formation between the salt and polymer has been studied by Fourier Transform Infrared (FTIR) spectroscopy. The high ionic conductivity of 1.27 × 10−3 S cm−1 at room temperature is achieved with the combination of 1.0 g i-carrageenan : 0.4 wt% LiCF3SO3 by AC impedance analysis. Total ion transference number estimated for the highest conducting sample is 0.95 by Wagner's DC polarization method and electrochemical stability of the same is 3.52 V by Linear Sweep Voltammetry (LSV) measurement. Lithium ion conducting battery has been fabricated using the highest conducting polymer membrane. Its open circuit voltage is measured as 1.70 V and its performance is studied.